The DEFTABLE macro unifies the interface to Common Lisp's table-like data structures (e.g., association lists, property lists, and hash tables, vectors), providing a concise, lightweight syntax. Later, when it's time to tune the performance of your program, you can specify how each table type will be implemented. For the purpose of this program, a table is anything you can put key/value pairs into and subsequently retrieve the value using the key.